240 THE CORONA.—DURATION OF THE COROLLA. 
monly situated at the junction of the claw and limb (fig. 501, a) ; 
or at the base of the petals (figs. 498 and 500). Such appendages 
may be well seen in the Mignonette (fig. 499), Crowfoot (fig. 
498), Lychnis (fig. 501, a), and Grass-of Parnassus (jig. 500). 
Similar scales may be also frequently noticed in monopetalous 
corollas near the throat, as in many Boraginaceous plants, for 
instance, the Comfrey, Borage, Forget-me-not (fig. 482, 7) ; and 
also in the Dodder, and many other plants. Sometimes these 
scales become more or less united and forma cup-shaped process, 
as in the perianth of the Daffodil (fig. 502) and other species of 
Narcissus ; to this the term corona is commonly applied, and the 
corolla is then said to be crowned. By many botanists, how- 
ever, this latter term is applied whenever the scales or appen- 
dages are arranged in the form of a ring on the inside of the 
corolla, whether united or distinct. The beautiful fringes on 
the corolla of the Passion-flower are of a similar nature. 
The origin of these scales is by no means clearly ascertained ; 
by some botanists they are supposed to be derived from the 
petals, by others to be abortive stamens ; but they are now 
more commonly regarded as ligules (see page 182) developed 
on the petals. Formerly many of these appendages were de- 
scribed under the name of nectaries, although but few of them 
possess the power of secreting the honey-like matter or nectar 
from which they derived their names ; they were therefore im- 
properly so termed. The nature of the so-called nectaries has 
been already described under the head of Glands (see page 71). 
DURATION OF THE CorotiA.—The duration of the corolla 
varies like that of the calyx, but it is almost always more fugi- 
tive than it. It is caducous if it falls as the flower opens, as in 
the Grape-vine ; commonly it is deciduous, or falls off soon after 
the opening of the flower. In rare instances it is persistent, in 
which case it usually becomes dry and shrivelled, as in Heaths 
and the species of Campanula (fig. 437), when it is said to be 
marcescent. 
Section 4. Tuer EssentTriaAL ORGANS OF REPRODUCTION. 
THE essential organs of reproduction are the androecium and 
gyncecium. and these together form the two inner whorls of the 
flower. They are called the essential organs because the action 
of both is necessary for the production of perfect seed. 
Flowers which possess both these organs are called hermaphro- 
dite or bisexual (fig. 518); when only one is present, they are wni- 
sexwal or diclinoris, as in the species of Carex (fig. 503), and Salix 
(figs. 415 and 416). The flower is also then further described as 
staminate or staminiferous (figs. 415 and 503) when it contains 
only a stamen or stamens ; and carpellary, pistillate, or pistilli- 
ferous, when it has only a carpel or carpels (jig. 416). Whena 
